The optimum mercury vapor pressure for producing a radiation of 2537 angstroms to excite a phosphor coating on the interior of a fluorescent lamp, which approximates six millitorr, at a corresponding mercury vapor temperature approximating 40 degrees C. To ensure optimum operation of the lamp at or about a mercury vapor pressure of six millitorr, the power density level of a conventional fluorescent lamp is adjusted to attain this result. A typical range of operating pressures may span from between four to seven millitorr. The lamp is typically designed such that the coolest location, (cooling point), in the fluorescent lamp is approximately 40 degrees C.
Compact fluorescent lamps, however, operate at higher power densities with the cold spot temperature typically exceeding 50 degrees C. As a result, the mercury vapor pressure is higher than the optimum four to seven millitorr range, and the luminous output of the lamp is decreased.
One consideration in controlling the mercury vapor pressure is to use an alloy capable of absorbing mercury from its gaseous phase in varying amounts, depending upon temperature. Alloys capable of forming amalgams with mercury have been found to be particularly useful. The mercury vapor pressure of such an amalgam at a given temperature is lower than the mercury vapor pressure of pure liquid mercury.
Positioning an amalgam to achieve a mercury vapor pressure in the optimum range remains difficult. For stable long-term operation, the amalgam should be placed and retained in a relatively cool location with minimal temperature variation. Such an optimal location is at or near the tip, or apex, of the lamp envelope.
As a practical solution, the amalgam support should maintain the optimal location of the amalgam, regardless of the orientation of the lamp.
The following prior art discloses the various aspects in the design of spirally shaped cold cathode fluorescent lamps.
U.S. Pat. No. 5,500,567, granted Mar. 19, 1996, to R. H. Wilson, et al., discloses an apparatus for securing an amalgam at the apex of an electrodeless fluorescent lamp, having a glass rod extending through and sealed to the exhaust tube of an electrodeless SEF fluorescent discharge lamp that has a metal support member at one end thereof for supporting an amalgam at or near the apex of the lamp envelope. The metal support member may comprise a spiral-shaped wire, a wire screen, or a wire basket. Preferably, the amalgam is maintained in contact with the apex of the lamp envelope. If desired, the metal support member may comprise a magnetic material to allow for magnetic transport of the amalgam assembly during lamp processing. The metal support member restricts spreading of the amalgam when in a liquid state; and the glass rod provides rigid support for the amalgam independent of lamp orientation.
U.S. Pat. No. 6,528,953, granted Mar. 4, 2003, to N. Pearson, et al., discloses an Amalgam retainer having an arc discharge lamp comprised of an arc chamber having an amalgam tip attached to and communicating with it. The communication comprises a narrow tubular extension that penetrates the amalgam tip for a distance less than the depth of the tip. An amalgam that includes bismuth is contained within the amalgam tip. This construction allows operation of the lamp in any position and prevents the bismuth in the amalgam from penetrating the lamp and poisoning the phosphor.
U.S. Pat. No. 6,630,779, granted Oct. 7, 2003, to J. Tokes, et al., discloses a fluorescent lamp wherein the discharge tube is bent substantially in plane. The fluorescent lamp is comprised of a discharge tube disposed substantially in a plane and shaped at least in part to define a substantial portion of the boundary of a zone in the plane. The part of the tube defining the boundary includes at least one straight portion. The discharge tube has a central axis and sealed ends provided with electrodes and at least two tube sections running substantially parallel to each other. Each tube section has at least one blind-sealed end and the tube sections are connected in series through bridges in the vicinity of the blind-sealed ends to define a single continuous discharge space to be excited by electrical power supplied to the electrodes. A lamp support housing is positioned within the zone and the ends of the discharge tube as well as the blind-sealed ends of the tube sections are re-entrant into the zone. The ends of the discharge tube are received in the lamp support housing. The lamp support housing carries means suitable for mechanically and electrically connecting to a socket and include lead-in wires connecting the electrodes directly or through an operating circuit to the means suitable for electrically connecting to a socket.
U.S. Pat. No. 6,633,128, granted Oct. 14, 2003, to Lilies, et al., teaches of a discharge lamp with spiral shaped discharge tube comprising a low-pressure discharge lamp with a double spiral shaped discharge tube including two spiral shaped tube portions. The tube portions define a central axis of the discharge tube. A cold chamber portion connects the ends of the spiral shaped tube portions. The cold chamber portion has a first transversal dimension substantially perpendicular to the central axis that is larger than the diameter of the tube portions. The cold chamber portion further has a second transversal dimension substantially parallel to the central axis. The second transversal dimension of the cold chamber portion substantially corresponds to the diameter of the tube portions.
U.S. Pat. No. 6,650,042, granted Nov. 18, 2003, to E. E. Hammer, discloses a low-wattage fluorescent lamp having at least one mercury cold spot region effective to maintain the mercury in the lamp at less than 30 degrees C., preferably 25. degrees C., in an enclosed lamp fixture. The lamp also features a reduced distance between electrodes resulting in less power being required to sustain an electric arc discharge during operation of the lamp. The lower power electric arc generates less heat to raise the temperature of mercury vapor within the lamp.
U.S. Pat. No. 6,731,070, granted May 4, 2004, to R. P. Scholl, et al., discloses a low-pressure gas discharge lamp having a gas discharge vessel containing a gas filling with a chalcogenide of the elements of the fourth main group of the periodic table of elements and a buffer gas, and having inner or outer electrodes and means for generating and maintaining a low-pressure gas discharge.
U.S. Pat. No. 6,741,023, granted May 25, 2004, to A. Pirovic, discloses an electrode shield for a fluorescent tanning lamp comprising an open cup encircling a filament or electrode increasing the service life of the fluorescent tanning lamp. The cup having an open end acts as a shield reducing the sputtering of impurities onto the glass tube and contaminating the phosphor surface. In one embodiment, the cup is electrically and thermally coupled to an electrode support. The life of the fluorescent tanning lamp is greatly increased despite the use of relatively high currents and large number of on and off cycles.
Therefore, what is needed is a double helical, compact fluorescent lamp that has a plurality of cooling points that will allow the lamp to operate in a vertical position, with the apex facing upwardly, or with the lamp mounted in a horizontal plane, in any rotatable angle about the horizontal axis of the lamp, without degradation of the luminous output of the lamp.
It is therefore an object of the present invention to provide a plurality of cooling points about the periphery of a bi-helical compact fluorescent lamp, said cooling points being arranged about the periphery of the spiraled coils to provide a constant luminous output of the lamp, regardless of its positional angle from the vertical axis of orientation.
It is another object of the present invention to provide a plurality cooling points about the periphery of a bi-helical compact fluorescent lamp, said cooling points being arranged about the inner periphery of the spiraled coils to provide a constant luminous output of the lamp, regardless of its positional angle from the vertical axis of orientation.
It is still another object of the present invention to provide a plurality cooling points about the periphery of a bi-helical compact fluorescent lamp, said cooling points being arranged about the periphery of the spiraled coils at the distal ends to provide a luminous output of the lamp, when operated in a horizontal plane, equivalent to its operation in a vertical position.
It is still yet another object of the present invention to provide a plurality cooling points about the periphery of a bi-helical compact fluorescent lamp, where at least one of said cooling points being arranged proximately at the vertex joining the spiraled coils to provide a luminous output of the lamp, when operated in a vertical position, equivalent to its operation in a horizontal plane.
It is yet still another object of the present invention to provide a cooling point chamber that is an enlargement of the diameter of the lamp tubing, the length preferably not exceeding five diameters, creating a chamber having an increased volume.
An additional object of the present invention is to provide a plurality of cooling point chambers that are shaped as ellipsoidal convexities along the periphery of the tubing.
Yet, another object of the present invention is to provide a plurality of cooling point chambers that are shaped as ellipsoidal convexities along the inner periphery of the tubing.
Yet still another object of the present invention to provide a plurality of cooling point chambers, whose enlargements increase the diameter of the tubing, to decrease the temperature of the mercury vapor where the mercury vapor condenses and is deposited in said respective cooling point.
It is a final object of the present invention to provide a plurality of cooling point chambers having a plurality of enlargements along the length of the tubing; said cooling point chambers being of any arbitrary, generalized geometrical shape whose function is to decrease the temperature of the mercury vapor so that the mercury vapor condenses and is deposited in said respective cooling point.
These and other objects, features, and advantages of the present invention will become apparent from reading the following detailed description, the accompanying drawings, and the appended claims.